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Question Number 28468 by tawa tawa last updated on 26/Jan/18
![Prove that for all values of u, the point [a cosh(u) , b sinh(u)] lies on the hyperbola whose equation is. (x^2 /a^2 ) − (y^2 /b^2 ) = 1 And that the tangent at that point is : (x/a) cosh(u) − (y/b) sinh(u)](Q28468.png)
$$\mathrm{Prove}\:\mathrm{that}\:\mathrm{for}\:\mathrm{all}\:\mathrm{values}\:\mathrm{of}\:\mathrm{u},\:\mathrm{the}\:\mathrm{point}\:\left[\mathrm{a}\:\mathrm{cosh}\left(\mathrm{u}\right)\:,\:\:\mathrm{b}\:\mathrm{sinh}\left(\mathrm{u}\right)\right]\:\mathrm{lies}\:\mathrm{on}\:\mathrm{the}\: \\ $$$$\mathrm{hyperbola}\:\mathrm{whose}\:\mathrm{equation}\:\mathrm{is}.\:\:\:\:\:\frac{\mathrm{x}^{\mathrm{2}} }{\mathrm{a}^{\mathrm{2}} }\:−\:\frac{\mathrm{y}^{\mathrm{2}} }{\mathrm{b}^{\mathrm{2}} }\:=\:\mathrm{1} \\ $$$$\mathrm{And}\:\mathrm{that}\:\mathrm{the}\:\mathrm{tangent}\:\mathrm{at}\:\mathrm{that}\:\mathrm{point}\:\mathrm{is}\::\:\:\:\frac{\mathrm{x}}{\mathrm{a}}\:\mathrm{cosh}\left(\mathrm{u}\right)\:\:−\:\:\frac{\mathrm{y}}{\mathrm{b}}\:\mathrm{sinh}\left(\mathrm{u}\right) \\ $$